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China Foundry 2013年第1期10卷 18-23页

作者： Wu Xiaofeng Wang Zhe Zhang Guangan Wu Fufa School of Materials Science and Engineering Liaoning University of Technology

Bi has a good modification effect on the hypoeutectic Al-Si alloy, and the morphology of eutectic Si changes from coarse acicular to fine fibrous. Based on the similarity between Mg2Si and Si phases in crystalline structure and crystallization process, the present study investigated the effects of different concentrations of Bi on the microstructure, tensile properties, and fracture behavior of cast Al-15wt.%Mg2Si in-situ metal matrix composite. The results show that the addition of the proper amount of Bi has a significant modification effect on both primary and eutectic Mg2Si in the Al-15wt.%Mg2Si composite. With an increase in Bi content from 0 to lwt.%, the morphology of the primary Mg2Si is changed from irregular or dendritic to polyhedral shape; and its average particle size is significantly decreased from 70 to 6 μm. Moreover, the morphology of the eutectic Mg2Si phase is altered from flake-like to very short fibrous or dot-like. When the Bi addition exceeds 4.0wt.%, the primary Mg2Si becomes coarse again. However, the eutectic Mg2Si still exhibits the modified morphology. tensile tests reveal that the Bi addition can improve the tensile strength and ductility of the material. Compared with those of the unmodified composite, the ultimate tensile strength and percentage elongation after fracture with 1.0wt.% Bi increase 51.2% and 100%, respectively. At the same time, the Bi addition changes the fracture behavior from brittle to ductile.

关键词： AI/Mg2Si composites casting Bi addition microstructural characterization tensile properties

Improved tensile properties of Mg-8Sn-1Zn alloy induced by minor Ti addition

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China Foundry 2016年第3期13卷 151-158页

作者： Wei-li Cheng Quan-wei Tian Rui Huo Liang Tian Shou-fan Rong Key Laboratory of Interface Science and Engineering in Advanced Materials Ministry of Education Taiyuan University of Technology Shanxi key Laboratory of Advanced Magnesium-Based Materials Taiyuan University of Technology School of Materials Science and Engineering Jiamusi University

In this study, the influence of minor titanium(Ti) addition on the microstructure and tensile properties of Mg-8Sn-1Zn based alloys were investigated by means of optical microscopy, X-ray diffraction, scanning electron microscopy, energy dispersive spectrometry, and tensile tests. The results showed that Ti can decrease the secondary dendrite arm spacing(SDAS). The tensile strength of the Mg-8Sn-1Zn-Ti alloys is initially increased by increasing the Ti content up to 0.09 wt.%, but subsequently decreased for further increase of Ti content. The improved tensile properties are attributed to the decreased SDAS and refi ned Mg_2Sn phases, as well as the increased fraction of tin(Sn) segregated regions. The tensile fracture surface of the studied alloys shows mixed characteristics of cleavage and quasi-cleavage fracture. Adding Ti does not significantly change the fracture mode of the studied alloys.

关键词： Mg-8Sn-1Zn alloy tensile properties titanium tin segregation

Section thickness-dependent tensile properties of squeeze cast magnesium alloy AM60

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China Foundry 2012年第2期9卷 178-183页

作者： Xuezhi Zhang Meng Wang Zhizhong Sun Henry Hu Department of Mechanical Automotive and Materials Engineering University of Windsor Windsor Ontario N9B 3P4 Canada

The development of alternative casting processes is essential for the high demand of light weight magnesium components to be used in the automotive industry, which often contain different section thicknesses. Squeeze casting with its inherent advantages has been approved for the capability of minimizing the gas porosity in magnesium alloys. For advanced engineering design of light magnesium automotive applications, it is critical to understand the effect of section thickness on mechanical properties of squeeze cast magnesium alloys. In this study, magnesium alloy AM60 with different section thicknesses of 6, 10 and 20 mm squeeze cast under an applied pressure of 30 MPa was investigated. The prepared squeeze cast AM60 specimens were tensile tested at room termperature. The results indicate that the mechanical properties including yield strength （YS）, ultimate tensile strength （UTS） and elongation （A） decrease with an increase in section thickness of squeeze cast AM6O. The microstructure analysis shows that the improvement in the tensile behavior of squeeze cast AM60 is primarily attributed to the low-gas porosity level and fine grain strucuture which result from the variation of cooling rate of different section thickness. The numerical simulation （Magmasoft） was employed to determine the solidification rates of each step, and the simulated results show that the solidification rate of the alloy decreases with an increase in the section thickness. The computed solidification rates support the experimental observation on grain structural development.

关键词： squeeze casting magnesium alloy AM60 tensile properties section thickness

Effect of mold temperature and casting dimension on microstructure and tensile properties of counter-gravity casting Ti-6Al-4V alloys

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China Foundry 2016年第1期13卷 9-14页

作者： Shou-yin Zhang Jin-shan Li Hong-chao Kou Jie-ren Yang Guang Yang Jun Wang State Key Laboratory of Solidification Processing Northwestern Polytechnical University Xi 'an 710072 China School of Aeronautic Manufacturing Engineering Nanchang Hangkong University Nanchang 330063 China

The cast Ti-6Al-4V alloy bars with different section sizes were fabricated by investment casting at counter-gravity condition with the mold temperatures of 300 ℃ and 650 ℃, respectively. The microstructure of the alloy was observed by means of OM and SEM, and the effect of mold temperature and casting dimension on tensile properties was studied. Results show that equiaxed grains are obtained regardless of the casting dimension. 13 grain size tends to increase with an increase in mold temperature. Hot isostatic pressing of the alloy was carried out for tensile properties＇ comparison. Room temperature tensile test results show that Ti-6Al-4V alloy produced via counter-gravity casting has good balance of strength and ductility after hot isostatic pressing （HIP）. The alloy shows higher ductility due to the elimination of porosity. In both cast and HIP status, the tensile strength is inclined to decrease with an increase in mold temperature, while the ductility is prone to slightly increase. Both the strength and ductility tend to decrease with an increase in the casting dimension.

关键词： Ti-6Al-4V counter-gravity casting tensile properties hot isostatic pressing

Effects of grain refinement on cast structure and tensile properties of superalloy K4169 at high pouring temperature

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China Foundry 2016年第2期13卷 101-106页

作者： Zi-qi Jie Jun Zhang Tai-wen Huang Lin Liu Hai-jun Su Yan-li Shi Heng-zhi Fu State Key Laboratory of Solidification ProcessingNorthwestern Polytechnical UniversityXi'an 710072China Xi'an Jiaotong University City College Xi'an 710072China

In order to improve the filling ability of large complex thin wall castings, the pouring temperature should be increased, but this will result in the grain coarsening. To overcome this problem, two kinds of grain refiners of Co-Fe-Nb and Cr-Fe-Nb ternary alloys, which contain high stability compound particles, were prepared. The effects of the refiners on the as-cast structures and tensile properties of the K4169 superalloy with different casting conditions were studied by analyzing specimens 110 mm long and 20 mm in *** showed that the mixture addition of the two refiners in the melt of K4169 can reduce the columnar grain region and decrease the equiaxed grain size greatly. After refinement, the amount of Laves phase decreases and its morphology changes from island to blocky structure. The carbides in the fine grain samples are fine and dispersive. Meanwhile, the porosity in specimens is decreased due to grain refinement. As a result, the yield strength, ultimate strength and the elongation of the specimens are increased. The grain refinement mechanisms are also discussed.

关键词： superalloy K4169 grain refinement tensile properties

Microstructure and tensile properties of thixo-diecast AZ91D magnesium alloy

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China Foundry 2013年第5期10卷 288-293页

作者： Ai Xiulan Quan Gaofeng Liu Zhaoming Gao Hong Liaoning Province Laboratory of Key Material for Railway Dalian Jiaotong University School of Material Science and Engineering Southwest Jiaotong University

The thixo-diecasting （TDC） process is the combination of semi-solid billet preparation technology and die casting technology. The TDC process not only keeps the characteristics of thixo-forming but also has high efficiency and low cost. In the present work, the microstructures and mechanical properties of an AZ91D magnesium alloy prepared by the thixo-diecasting （TDC） process were characterized in as-cast condition. The TDC alloy produced exhibits a unique microstructure containing a-Mg solid solution and/3-Mg^TAI^2 intermetallic compound, and there are some small droplets and a small gray globule with eutectic structure in the primary a-Mg grains. The ultimate tensile strength and elongation of the TDC alloy also increase in comparison with other processes, such as thixocasting. Fracture surface observation shows that a crack mainly originates from the brittle fracture of the eutectic phases. The deformation of ductile a-Mg phase provides the TDC alloy with the main strain.

关键词： AZ91D magnesium alloys semi-solid thixo-diecasting microstructure tensile properties

Microstructure and tensile properties of low cost titanium alloys at different cooling rate

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Rare Metals 2012年第6期31卷 531-536页

作者： Wang Guo Hui Songxiao Ye Wenjun Mi Xujun Wang Yongling Zhang Wenjing Gen Res Inst Nonferrous Met State Key Lab Fabricat & Proc Nonferrous Met Beijing 100088 Peoples R China

Titanium and titanium alloys have several advantages, but the cost of titanium alloys is very expensive compared with the traditional metal materials. This article introduces two new low-cost titanium alloys Ti-2.1Cr-1.3Fe (TCF alloy) and Ti-3Al-2.1Cr-1.3Fe (TACF alloy). In this study, we used Cr-Fe master alloy as one of the raw materials to develop the two new alloys. We introduce the microstructure and tensile properties of the two new alloys from β solution treated with different cooling methods. Optical microscopy (OM), X-ray diffractometry (XRD), and transmission electron microscopy (TEM) were employed to analyze the phase constitution, and scanning electron microscopy (SEM) was used to observe the fracture surfaces. The results indicate that the microstructures consist of β grain boundary and α′ martensite after water quenching (WQ), β matrix and α phase after air cooling (AC) and furnace cooling (FC), respectively. Also, the microstructure is the typical basketweave structures after FC. Of course, athermal ω is also observed by TEM after WQ. The strength increases with decreasing cooling rates and the plasticity is reversed. Because of the athermal ω, the strength and ductility are highest and lowest when the cooling method is WQ. The strength of TACF alloy is higher than the TCF alloy, but the plasticity is lower. The fracture surfaces are almost entirely covered with dimples under the cooling methods of AC and FC. Also, we observe an intergranular fracture area that is generated by athermal ω, although some dimples are observed after WQ.

关键词： titanium alloys microstructure martensite tensile properties fracture morphology

Manufacture of Flax Reinforced PP Laminates and Research on the tensile properties

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Journal of Donghua University(English Edition) 2007年第3期24卷 362-366页

作者：刘丽妍黄故王瑞 School of Textiles Tianjin Polytechnic University

Flax fiber was used to reinforce Polypropylene （PP） owing to its lower impact on environment and suitable mechanical behaviors. To overcome the difficulty of penetrating fibers due to the high viscosity of thermo-plastic resin, PP filaments wrapping around the linen yam produced commingled yams, which were woven into fabrics as preforms to make laminates by optimum hot-pressing technology. The effects of fiber volume fraction, fabric density and structure on tensile properties of composites were researched through analyzing the tensile test results and the scanning electronic microscope （SEM） micrographs of fracture surface. Conclusions are drawn that the properties of laminates with fiber volume fraction of 0.50 are better than those with the other two fractions. For plain structure, the tensile properties in warp direction decrease according to the increase of weft density while in weft direction increase. For different fabric structures, properties of laminates with structures of plain 3, twill 2/2 and twill 3/1 increase gradually. And properties in weft direction are prior to those in warp direction for each laminate.

关键词： flux Polypropylene composites technologicalparameters tensile properties

Influence of Homogenization on the Microstructure and tensile properties of Extruded Mg-Zn-Zr-RE Alloy

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Journal of Rare Earths 1991年第2期9卷 125-128页

作者：陶春虎张少卿鲁立奇 Institute of Aeronautical Materials Beijing 100095China

The microstructure and tensile properties of the extruded Mg-Zn-Zr-RE alloy bars are *** extruded bar without previous homogenization has the highest tensile strength,whereas the tensile strength of the extruded bar previously homogenized at 400℃ or 380℃ is *** long time homogenization,the trans- formation of rare earth compounds Mg_3REZn_6(Z phase)and Mg_3RE_2Zn_3(W phase)into Mg_(41)RE_5 and Mg Zn phases occurr and the MgZn phase grow *** addition,the dynamic recrystallization takes place in sub- sequent extrusion that caused decrease of the tensile strength.

关键词： Magnesium alloy Rare earth Microstructure tensile properties Homogenization

Micromechanical analysis on tensile properties prediction of discontinuous randomized zalacca fibre/high-density polyethylene composites under critical fibre length

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Theoretical & Applied Mechanics Letters 2020年第1期10卷 57-65页

作者： Dody Ariawan Eko Surojo Joko Triyono Ibrahim Fadli Purbayanto Agil Fitri Pamungkas Aditya Rio Prabowo Department of Mechanical Engineering Universitas Sebelas MaretSurakarta 57126Indonesia

In this research,the tensile properties'performance of compression moulded discontinuous randomized zalacca fibre/high-density polyethylene under critical fibre length was analysed by means of experimental method and micromechanical *** investigations were used to verify the tensile properties models toward the effect of fibre length and volume fraction on the *** experimental results showed that the tensile properties of composites had significantly increased due to the enhancement of fibre *** the contrary,a decline in the tensile properties was observed with the increase of volume fraction.A comparison was made between the available experimental results and the performances of Tsai-Pagano,Christensen and Cox-Krechel models in their prediction of composites elastic *** results showed that the consideration of fibre's elastic anisotropy in the Cox-Krenchel model had yielded a good prediction of the composites modulus,nevertheless the models could not accurately predict the composites modulus for fibre length study.

关键词： Zalacca fibre Micromechanical analysis High-density polyethylene Critical fibre length tensile properties